In a business application, it is often crucial to ensure that one projects a "professional" or businesslike image. When using a telephone, the telephone manner will influence this image, but the quality of the transmitted voice will also play a role.
On a traditional (wired) business telephone, the speaker's voice is returned to the speaker's ear via sidetone, so that the speaker can be aware of the quality (e.g. loudness) of his or her own voice. With this wireline connection there is typically little, if any, interference on the line that is under the dynamic control of the user, although one may choose to purchase a better quality telephone to project a better image or to abandon a call and try again if the line quality is poor.
When using a handsfree telephone, the transmitted voice often sounds "hollow" or "tinny" to the far end, a result of the increased separation between the mouth of the speaker(s) and the microphone. This "barrel effect" is a frequent source of complaint from users and is also an area where a competitive advantage may be gained by improving transmitted voice quality.
Because wireless devices are typically hand-held (bringing the microphone close to the mouth), the "barrel effect" is not usually a problem. However, as experience with wireless devices increases, evidence is accumulating that transmitted voice quality can be a serious concern in business application, to the extent that one may use a wireless device to receive calls but not to voluntarily initiate calls because the client/customer at the far end will be put off by the poor quality of some connections.
Unlike with a wired telephone, the quality of the low-power radio/wireless link is not fixed on a per-call basis but can be affected by the movements of the user or changing environmental conditions. For example, by walking a few feet or simply turning around the user may significantly alter the quality of the transmitted voice. The quality of the transmitted voice is also affected by interference through the radio link by noise, unwanted signals, or, of course, malfunction, low battery etc. of the handset. Because the user has no means of knowing the effect of these conditions on the transmitted voice, other than by asking the far end, it would be advantageous to provide a mechanism for the user to receive feedback about transmitted voice quality. This mechanism will, in turn, "train" the user to behave in ways which will maximize the "professionalism" of his or her image by improving transmitted voice quality.
In U.S. Pat. No. 5,014,294, issued May 7, 1991 to Kromenaker et al, a unique speakerphone for a cellular telephone is disclosed. The speakerphone of the patent includes means for preventing howl. In addition to the problem of the "barrel effect" mentioned above, the speakerphone also suffers from howling, particularly when used in a confined space such as a car. The howling is caused by acoustic coupling between the microphone and the speaker at the portable terminal because the land link to which the base station is wire-connected contains acoustic feedback and hybrid mismatch feedback elements and completes the loop. In the patent, an A/D converter samples the transmitted and received signals at the portable terminal and a microcomputer operates mute gates on the transmit and receive paths to prevent howling. No signal analysis of the received signal takes place at the base station and no processed signal of the received signal is sent back to the portable terminal to indicate the quality of the radio/wireless link monitored at the base station.
U.S. Pat. No. 4,939,766, issued Jul. 3, 1990 to Umemoto et al, discloses a radio telephone system in which a threshold level of the received signal strength at the handset can be modified arbitrarily. The threshold level is provided to indicate when the received signal strength reaches the minimum level to maintain the quality of radio/wireless link. The indication is done visually or audibly. The received signal is measured at the handset. No indication as to the quality of the radio/wireless link of the signal received at the base station is fed back to the portable terminal.
It should also be noted that visual indication of voice quality (e.g. via green, yellow, and red LEDs) is often impractical in a wireless setting, as it is often impossible to position visual indicators where they can be seen while speaking on a device that has been designed to be small and held against the ear. However, such visual indicators may be useful under certain circumstances and the device can be easily designed to include those features.